IV.9.2.1 Frozen plasticity may also play an important role in some processes at an intraspecies level. Cultivated plants include both autogamous (e.g. wheat) and also heterogamous (e.g. rye) species and varieties. It follows from the theory of frozen pla

Cultivated plants include both autogamous (e.g. wheat) and also heterogamous (e.g. rye) species and varieties.It follows from the theory of frozen plasticity that the properties of heterogamous species and varieties should be more stable on a micro-evolutionary scale than the properties of autogamous species or even varieties that reproduce predominantly or only vegetatively (Flegr 2002).In the former case, the alleles are in the presence of other alleles in each generation, so that their selection coefficient changes unpredictably.Thus, it is difficult for selection pressure to act consistently leading to their elimination or fixation.In contrast, for autogamous or vegetatively reproducing species, the genetic environment of the individual alleles is the same in each generation and thus the selection value remains stable from one generation to the next.Thus, the genetic composition of the population can easily submit to the effect of selection through evolutionary changes.

The different response capacity of sexual and asexual (and autogamous) species and varieties for selection pressures is apparently also very important in plant improvement and normal farming practice.It is relatively difficult to select new varieties in sexually reproducing species (or amongst the above-mentioned heterogamous plants).In order for the organisms to respond to the relevant selection pressures, it is mostly necessary to work with relatively small populations and to employ a high degree of inbreeding, to reduce as far as possible the genetic variability of the population and thus to increase the heritability of the phenotype manifestations of the relevant selected alleles.In asexual (and autogamous) species and varieties, it is possible and, because of the relative lack of genetic variability, frequently also necessary to perform selection in large populations.On the other hand, the newly obtained varieties are more stable for sexual (and heterogamous) varieties than for varieties reproducing asexually or autogamous varieties.Their advantageous properties should not gradually disappear as a consequence of the action of natural selection, which constantly increases the biological fitness of the organisms, frequently at the expense of their usefulness (Flegr 2002).

As, until recently, these phenomena had practically no support in genetic or evolutionary theory, they are very rarely described in the biological literature.The publications of the Lysenkoists constitute an exception; these results follow very well from consideration of their absurd theories.In their work, these Soviet “researchers” described the low stability of the evolutionary properties of autogamous varieties of cereals compared to heterogamous varieties and also promoted agrotechnical procedures based on intraspecies crossing of autogamous plants, which led to prolonged maintenance of the useful properties of the given varieties (Lysenko 1950).It is probable that a major part of the results published by Lysenkoists were falsified or even fabricated and it is, understandably, necessary to approach their data with a maximum of caution (Medveděv 1969).Nonetheless, it is not possible to completely ignore the fact that a certain part of the information was passed down from the experienced empirical agronomists of previous generations.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.